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111.
计及二阶效应的门座起重机变幅工况动力学分析 总被引:1,自引:0,他引:1
对门座起重机的变幅工况进行了计及二阶效应的大范围运动弹性动力分析。使用柔性多体系统动力学方法描述柔性体的变形和运动,结合非线性有限元理论推导了一般运动柔性单元在局部坐标系下的计及二阶效应的动力学方程,进而使用三结点Euler-Bernoulli梁单元的形函数,推导了柔性梁单元的动力学方程。对该方程进行静力凝聚并使用随动坐标法,得到便于系统动力学方程组集的整体坐标系下的两结点梁单元动力学方程。对某型门座起重机臂架系统的变幅工况进行了计及二阶效应的弹性动力分析,结果表明:二阶弹性位移和内力均为相应线性解上的波动,且波动幅值较大,因此对大柔度重载机械应进行考虑二阶效应的弹性动力分析。 相似文献
112.
A vu-decomposition method for solving a second-order cone problem is presented in this paper. It is first transformed into a nonlinear programming problem. Then, the structure of the Clarke subdifferential corresponding to the penalty function and some results of itsvu-decomposition are given. Under a certain condition, a twice continuously differentiable trajectory is computed to produce a second-order expansion of the objective function. A conceptual algorithm for solving this problem with a superlinear convergence rate is given. 相似文献
113.
基于模态分析法的载荷识别方法利用模态矩阵获得系统的非耦合形式,推导单自由度系统的载荷识别公式,但要求系统为比例阻尼。在模态模型基础上,对一般系统建立基于二阶系统解耦的动载荷时域识别模型。首先,利用基于Lancaster结构的二阶系统解耦方法推导出系统的非耦合形式;然后,采用精细逐步积分方法,在载荷为阶跃力的假设下,推导出载荷识别数学公式;最后,由系统实时响应反求结构载荷的时间历程。数值算例验证了本文方法针对比例阻尼系统较模态模型具有更高的精度,而且对非比例阻尼系统也有效可行。 相似文献
114.
115.
J. Magnaudet 《Applied Scientific Research》1993,51(1-2):525-531
In this paper we propose a new rational model for turbulent transport of Reynolds stresses and dissipation. For this purpose we first analyse some properties of diffused turbulence i.e. turbulence where dissipation is balanced by turbulent diffusion arising from inhomogeneity. Then we use some of these results to deduce some mathematical requirements that must be satisfied by any rational model and we show that they are not verified by available models. Consequently we derive a more general model taking into account the various properties of diffused turbulence. 相似文献
116.
The purpose of this research is to further investigate the effects of material inhomogeneity on the decay of Saint-Venant
end effects in linear isotropic elasticity. This is carried out within the context of anti-plane shear deformations of an
inhomogeneous isotropic elastic solid. The mathematical issues involve the effects of spatial inhomogeneity on the decay rates
of solutions to Dirichlet or Neumann boundary-value problems for a second-order linear elliptic partial differential equation
with variable coefficients on a semi-infinite strip. In previous work [1], the elastic coefficients were assumed to be smooth
functions of the transverse coordinate so that the material was inhomogeneous in the lateral direction only. Here we develop
a new technique, based on a change of variable, to study generally inhomogeneous isotropic materials. The governing partial
differential equation is transformed to a Helmholtz equation with a variable coefficient, which facilitates analysis of the
influence of material inhomogeneity on the diffusion of end effects. For certain classes of inhomogeneous materials, an explicit
optimal decay estimate is established. The results of this paper are applicable to continuously inhomogeneous materials and,
in particular, to functionally graded materials.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
117.
Pollutant dispersion under unstably stratified atmosphere was investigated numerically using the finite element method. The effects of atmospheric stability on plume trajectory were studied using a three-dimensional second-order closure dispersion model. The numerical model was implemented using domain decomposition method and carried out using a parallel computer. The computation accelerates significantly and the size of computation can be largely increased as a result of the parallelism. A passive contaminant point source was placed at the middle of the convective boundary layer to simulate the atmospheric dispersion. The requirement of the input of dispersion coefficients in k-theory and Gaussian models was replaced with direct input of turbulence flow data. It was found that the present numerical model can predict several non-Gaussian plume behaviours and the computed results agreed well with findings from experimental observations. © 1998 John Wiley & Sons, Ltd. 相似文献
118.
119.
Pawel Kröger 《Journal of Theoretical Probability》1990,3(4):515-531
We prove comparison theorems for diffusion processes onR
d. From these theorems we derive lower and upper bounds for the transition probabilities of a diffusion process. In contrast to the known estimates for fundamental solutions of parabolic equations our bounds do not depend on the moduli of continuity of the coefficients of the differential operator. 相似文献
120.
Eva B. Vedel Jensen 《Annals of the Institute of Statistical Mathematics》1991,43(3):455-468
Recent developments in the stereological analysis of particles are reviewed. The trend has been towards methods which are applicable without specific assumptions about particle shape. Geometric samples of a local 3-d character are used. Stereological estimators of particle intensity, particle size distribution and particle interaction are presented and discussed.An earlier version of this article was presented at the Symposium on the Analysis of Statistical Information held in the Institute of Statistical Mathematics, Tokyo during December 5–8, 1989. 相似文献